This invention relates to household refrigerators of the type having a fresh food storage compartment and a freezer or freezing compartment above the fresh food compartment. More particularly it relates to such refrigerators in which air is chilled by a separate evaporator, with a portion of the cold air being circulated through the freezer compartment and another portion of the cold air being circulated through the fresh food compartment.
In some prior art refrigerators, such as disclosed in U.S. Pat. No. 3,379,029-King, assigned to General Electric Company, assignee of the present invention, there is provided an upper freezing compartment and a lower fresh food compartment separated by a horizontal insulating partition. An evaporator chamber is formed at the rear of the freezer compartment. The fan in the evaporator chamber draws air from each of the freezer compartment and the fresh food compartment into the evaporator chamber where it mixes and passes over the evaporator. The fan discharges the chilled air from the evaporator chamber into the freezer compartment and a portion of this air then goes into the fresh food compartment. As the air flows through the freezer and fresh food compartments, particularly the fresh food compartment, it absorbs moisture. Then, as it passes over the evaporator much of the moisture condenses out and deposits as frost on the evaporator coils. In order to keep the evaporator in proper working condition this frost periodically must be melted and removed from the evaporator chamber. Because of the low temperture in the evaporator chamber this defrosting step must be repeated fairly often and care must be taken to assure that the temperature of the adjacent freezer compartment does not rise too much during defrost operations.
In accordance with the present invention a construction is provided in an improved refrigerator wherein a duct is formed at the rear of the fresh food compartment for returning air from the fresh food compartment to the evaporator chamber. Another section or extension of the evaporator is positioned in this duct and precools the fresh food return air. Preferably the evaporator extension is effective to cool the fresh food return air to about the same temperature as the freezer return air. This arrangement more effectively utilizes the capacity of the refrigerant.
Most of the moisture in the fresh food return air condenses and deposits on the evaporator extension as frost. When the compressor turns off the duct and the evaporator extension warm-up the frost melts and is disposed of. Since the fresh food return air contains most of the moisture, less frost is deposited on the evaporator section in the evaporator chamber and more time can elapse between defrost operations.